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Re: LANG: owl:import - Two Proposals

From: Jonathan Borden <jonathan@openhealth.org>
Date: Tue, 1 Oct 2002 20:22:36 -0400
Message-ID: <05e701c269a9$cf4aa3c0$7c674544@ne.mediaone.net>
To: "Jeff Heflin" <heflin@cse.lehigh.edu>, "Jim Hendler" <hendler@cs.umd.edu>
Cc: "WebOnt" <www-webont-wg@w3.org>

Jeff Heflin wrote:


> In [1], I listed what I consider to be a number of problems with
> proposal #2. I haven't heard anyone address any of these concerns. If
> these were addressed satisfactorily (perhaps by an alternate proposal)
> then I would be happy to endorse that approach.
>

I've suggested what may be an alternate approach, or simply a wrinkle on #2
in http://lists.w3.org/Archives/Public/www-webont-wg/2002Sep/0519.html

Regarding your objections:

[[
Cons:
- Having valid syntax that has undefined semantics may lead to reduced
interoperability. In particular, some users may build ontologies that
rely on the arbitrary decisions made by their favorite tool vendors.
]]

I'm unsure how to interpret this statement. I would say that the OWL
processor should include triples obtained by retrieving and parsing the
_object_ of an owl:imports statement, into the current "graph", but that any
URIref ought be retrieved and/or parsed only once.

Is that 'semantics' undefined? (seems precise enough for me :-)

[[
- It is unclear what it should mean if a document C contains the
statement A owl:imports B. Should this be another undefined construct?
If so, how can you determine from a graph if the subject of an imports
statement is the URI of the document from which the imports statement
comes?
]]

Fair question, and one open for discussion. I'd say that regardless of the
subject, the object be imported into the current graph/KB.

[[
- The fact that an ontology's classes and properties do not occur
between the <Ontology> tags is unintuitive
]]

Oh well. That's an artifact of the decision to use RDF, however we decided
to use RDF/XML at F2F 2.

[[
- The use of about="" to make statements about the enclosing document
seems like a hack. In particular is seems like we could be confusing the
notion of a document that describes an ontology and the concept of an
ontology itself.
]]

Maybe, but what is the functional significance of this, and what requires us
to use rdf:about=""?

[[
- The approach only partially succeeds in its goals, because although it
represents ontologies and their properties, it loses the ability to
recognize the boundaries of an ontology (i.e., what it contains) as soon
as two or more graphs are merged together. In particular, if this
approach is extended for use with versioning, then we lose the ability
to know which statements come from which version of an ontology.
]]

Perhaps, but is the ability to recognize the boundaries of merged ontologies
a requirement, or objective? That's to say, is meeting the above proposed
goals worth major changes to the OWL syntax, ones that go against RDF
compatibility?

It seems that this issue is a general one with software modules e.g. when
they are compiled together, it's hard to know what came from where unless
out of band information, such as used by debuggers, is included. Yet ANSI
C++ is ANSI C++.

Jonathan
Received on Tuesday, 1 October 2002 20:40:45 GMT

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